Concentrating solar collector and pre-formed fresnel array reflector panel

ABSTRACT

A concentrating solar collector is disclosed, comprising: A nested main frame and reflector carriage with vertically folding reflectors in a Fresnel-type array, using a one-piece pre-formed panel. A hand-winch operated cable system provides for a full range of reflector altitude adjustment. A one-piece, pre-formed reflector panels provide for pre-aligned mounting of reflective material. An alignment guide allows assessment of solar tracking alignment without gazing toward the focal area. A flattop receiver for heating smaller flat-bottomed pots and pans or for direct griddle cooking, and an adjustable rack for positioning larger cooking vessels in the focal area for use as direct receivers. Also described is a method for making one-piece, pre-formed reflector panels. One embodiment has a lower frame portion substantially forming a rolling chassis. An additional embodiment describes lower frame structure for a fixed location installation.

CROSS-REFERENCE TO RELATED APPLICATIONS

Not Applicable

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable

REFERENCE TO SEQUENCE LISTING, TABLE OR COMPUTER PROGRAM LISTING

Not Applicable

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to distributed-scale apparatus for concentrationand collection of solar energy.

2. Discussion of Prior Art

As non-renewable energy resources such as coal, oil, and natural gasbecome more scarce and costly to obtain, the need for practical ways toutilize renewable energy sources grows. Solar energy investment inindustrialized regions has been influenced by preexisting patterns andinfrastructure for distribution of electrical power from large,centralized facilities. Several large facilities for centralized solarthermal generation of electric power have been completed in the US andother countries. These have typically used a great number ofground-based heliostats to reflectively concentrate solar energy to afocal area containing a tower-mounted receiver. Thermal energy collectedby the receiver is then is transferred to drive nearby steam turbinesfor generation of electric power, which is then fed into to the existinggrid for distribution. Energy consumers in some areas have installedlocal systems, which avoid the transmission losses inherent indistribution from centralized plants, but usually operate at the lowerefficiency of photovoltaic (PV) conversion. Locally collected solarthermal energy is also used for heating buildings or adjunctively toheat water. Such systems offer greater efficiency, avoiding both energytransmission and conversion losses. Local apparatus for concentratingsolar thermal energy is much less common, though cooking is onerelatively popular use.

Many less-developed areas of the world have seen significantdeforestation and environmental degradation as a result of people usingtraditional fuels for cooking fires. Efforts have been made to encourageuse of solar cookers in these areas, with limited success. However,there is an increasing need to encourage local use of solar energy inmore industrialized regions, also. Populations with a lifestyle andeconomy that are more dependent upon fossil fuels will suffer greaterstress, as those fuels become more costly. To the extent that means forrenewable energy use are familiar and available to those populations,difficulties stemming from a culture of dependence upon fossil fuel canbe mitigated.

Development and implementation of apparatus for local scale, distributedsolar thermal energy collection and use confronts many of the samedifficulties as large-scale installations. Apparatus for localconcentration of solar energy offers a greater range of uses thannon-concentrating solar collectors, but presents a greater challenge fordesign and cost efficiency. Beyond the costs of materials, manufacturingand maintenance, development of apparatus suitable for home, farm, orsmall business use also contends with issues such as space requirements,safety, portability and ease of use.

Prior art in this area has sometimes employed focusing lenses forconcentration; an example is U.S. Pat. No. 4,913,130 (Inagaki, Sawata.)Reflecting concentrators have been more common, tending to be lesscostly. However, the incident angle of sunlight to a lens or reflectorthat is fixed in position will change continuously as the earth turns,thus changing the resulting reflective angle. A concentrator apparatustherefore must track the apparent movement of the sun across the sky, inorder to achieve concentration of incident light to the desired target,or focal area, where the receiver of the apparatus is located.

Solar tracking by a concentrator must be done through two axes,corresponding to altitude and azimuth of the sun's apparent position inthe sky. Maintenance of automated mechanical solar tracking has been asignificant cost barrier for large, centralized solar thermal electricgeneration facilities. Concentrators with individually movingreflectors, even at a smaller scale, require a complicated mechanicalinfrastructure. An example is in U.S. Pat. No. 6,945,246 (Kinoshita).

However, smaller scale concentrators may also use reflective surface inthe shape of an elliptic paraboloid, or a plurality of flat reflectorsin a Fresnel array approximating the same effect. Such reflectors moveupon a common framework to track the sun. This arrangement simplifiesthe mechanical infrastructure needed. “Parabolic dish” reflectors havebeen assembled from wedge-shaped sections of flat, polished sheet metalthat are placed into a special curved frame to approximate a paraboloidshape, such as in U.S. Pat. No. 3,797,476 (Tarcici), and U.S. Pat. No.6,863,065 (Marut, Brunette). An example of such parabolic dishconcentration that has seen some commercial success is the GermanSK-series of cookers, designed by Dr. Dieter Seifert of EG Solar. At thetime of this writing, information was accessible via:http://solarcooking.wikia.com/wiki/SK14. A similar design had begunproduction commercially in the US at the time of this writing, under thename “Sun Power Cooker” and information was accessible via:http://sunpowercooker.com/.

In dish type concentrators the receiver and the user can cast shadowsover reflector area in some designs, reducing efficiency. Cookingvessels positioned over reflectors, or that must be lifted over them aremore likely to may spill and spatter food upon the reflectors, alsoreducing efficiency. Some designs have partial paraboloid reflectorsseparated and foldable for storage or transport. An example of this is aparabolic cooker that has been subsidized and promoted by government inChina, known as the Ao Chi F800. At the time of this writing,information was accessible via: http://solarcookingwikia.com/wiki/Ao ChiSolar Cooker. The Ao Chi F800 reflective surface is not very durable,being a metallized plastic film. The film is produced in a flat sheet,and adhered to the curved, pre-cast paraboloid section after cutting thefilm into small pieces, to minimize wrinkles in the material. Thereceiver sits above the reflector area, with the resultant problems ofspillage. This unit is also limited in its reflector size and power, infavor of user access to the receiver.

User access to the receiver for cooking-related activity becomes moreproblematic as the size of reflectors is increased for greaterconcentrator capacity. Similarly, the challenge of providing aconvenient way to perform manual solar tracking adjustments grows inproportion to reflector area.

Fresnel reflector designs have been produced for the purpose of reducingreflector bulkiness and cost, such as in U.S. Pat. No. 4,350,412(Steenblik) and U.S. Pat. No. 4,561,425 (Long, Ware). However, theseimplementations still require costly, laborious and difficultfabrication techniques, or lack a surrounding structure that providesgood ease of use.

The prior art known to the applicant that is nearest in form to thecurrent invention was based upon the “Papillon” Solar Cooker, developedby Jochen Dessel and Prof. Bernd Hafner of the Solarinstitut Jüich(Germany.) At the time of this writing, information on the Papillon wasaccessible at: http://solarcooking.wikia.com/wiki/Papillon andhttp://www.solar-papillon.com/. The Papillon has two reflector sections,similar to the Ao Chi design, but separated further from each other by asizeable gap, with the receiver positioned above the gap. This avoidsshadowing and food spillage problems. The Papillon's reflectors are ofpolished sheet aluminum in strips, fitted to a curved frame toapproximate a continuous paraboloid section. Fabrication and assembly iscostly, the paraboloid section shape is rather bulky, and the userapproach to the focus becomes difficult when the sun is lower in thesky. The altitude adjustment mechanism of the Papillon comprises asliding-groove and pinch-bolt device to attain and hold reflectorposition. The location of the mechanism is inconvenient and possiblyhazardous to the user, as it requires reaching over the focal area pasta hot cooking vessel. Azimuth adjustments require tilting the entireapparatus to pivot it upon its one axle or skidding its base footsideways, risking spillage from the vessel at the focal area.

Lorin Symington of the Canadian non-profit corporation ASTRA modifiedthe Papillon design, in part by using flat glass mirrors in aFresnel-type array. This design was dubbed the “Iron Butterfly,” anddemonstrated in West Africa in 2008. At the time of this writing, photodocumentation was accessible via:http://solarcooking.wikia.com/wiki/Butterfly_(Iron).

The Iron Butterfly's reflector arrays are in a trapezoidal shape thatdoes not maximize reflector aperture relative to outer dimensions of theapparatus, in use or in the (folded) storage position. Mounting andaligning the Fresnel array of mirrors requires a complex and heavybacking structure. A backing plate for each flat reflector in the arraymust be aligned and attached to framing with individual welded supports,making fabrication laborious and costly, and adding substantially to theweight of the apparatus. Information on the process for making the IronButterfly's reflector panels was accessible at the time of this writingvia: http://www.astraonline.ca/?p=SFT. Though some success has beendemonstrated, the difficult and laborious multi-step process isvulnerable to error and imprecision at various stages.

The Iron Butterfly's parallel-square reflector carriage features crossbracing removed to one end of the carriage, so that the user can closelyapproach and reach the focal area from the opposite end when the sun isat lower altitudes. But flexing and distortion of the non-braced portionof the carriage may reduce focal precision and usable energy, and thefacilitation of user proximity to the focal area increases thelikelihood of operator exposure to concentrated solar energy. Thebracing location also limits the range of carriage travel; with the sundirectly overhead, proper focus requires compensatory tilting of theentire apparatus. The Iron Butterfly's spooling mechanism forcable-controlled adjustment of reflector altitude is located near thefocal area, similar to the Papillon design, so use is difficult andpossibly hazardous. It requires the user to reach over the focal areaand past a hot cooking vessel, or to walk around to the opposite side ofthe apparatus and duck or reach under reflector positioning lines, whilestepping over the chassis/wheels. As in the case of the Papillon,azimuth and altitude adjustment also require the operator to gazedirectly at the focal area to gauge the location and intensity ofconcentrated sunlight. The user position of the Papillon and IronButterfly is on the same side of the receiver that reflected,concentrated solar energy strikes when the sun is at lower altitudes, sothat diffuse reflection to the user is greater. Protective eyewear maymitigate the discomfort and possible hazard of intense solar radiationreflected from the receiver to the user's eyes. However, positionaladjustments are difficult and uncomfortable to perform accurately inthis manner, further compromising ease of use and general efficacy ofthe concentrator.

Suspension lines to hold the Iron Butterfly's reflector panels inoperating position are attached to the panel carriage asymmetrically andlack a means to maintain equal tension between them. This may contributeto flexion of the reflector panels with consequent focal imprecision.

BRIEF SUMMARY OF THE INVENTION

My solar collector in its preferred embodiment provides a nested frameand reflector carriage with vertically folding reflector panels. Thelower frame geometry facilitates a novel cable system for a full rangeof reflector adjustment by easy, manual operation. The reflectors swingaway from the user's position, so that concentrated energy strikes theopposite side of the receiver and minimizes exposure of the user todiffuse reflection. Also provided is a Fresnel-type reflector supportpanel composed of a single, preformed piece, with integral, pre-alignedmounting surfaces for flat reflective material. This eliminates theheavy backing structure of prior art, and permits simpler and lesscostly assembly of a Fresnel reflector array. The reflector supportpanels, carriage, frame and cable system permit a larger, more preciselyfocused reflector area to fold to a relatively compact size for storageor portability. An adult user of ordinary physical capability caneasily, quickly and comfortably make positional adjustments toreflectors, from the same safe position in which cooking activity isperformed. The solar collector further includes an alignment guideplaced away from the focal area, obviating repeated exposure of a user'seyes to receiver glare during reflector adjustments. It further providesa flattop receiver that shields the user from glare, providing a flat,horizontal surface where flat-bottomed pots and pans can be heated, ason a smooth-top stove. The flattop receiver also provides a griddle-likedirect cooking surface. An additional support rack adjusts to suspendlarger pots and pans of various sizes in the focal area for directheating.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a perspective view of the preferred embodiment from the frontof the solar collector, with the flat top receiver in place andreflector panels positioned for overhead sun.

FIG. 1 a is a perspective view from the front of the preferredembodiment, with the pot and pan rack supporting a large saucepan, andreflector panels adjusted for a lower sun position.

FIG. 1 b is a view from the rear of the solar collector, showingreflector panels upright for storage and held in position by a commonlanyard, with a stockpot on the pot and pan rack.

FIG. 2 is a perspective view from the rear of the main frame of thepreferred embodiment.

FIG. 2 a is a detail view from the rear, of the upper portion of themain frame.

FIG. 2 b is a side view of an additional embodiment of the main frame,with a ground-based pivot for installation of the solar collector in afixed location.

FIG. 2 c is an exploded detail view of an additional embodiment:Ground-based pivot.

FIG. 3 is a perspective side-view of the altitude cable system.

FIG. 4 is a perspective view from above and rear, of the solar collectorwith reflector panel carriage.

FIG. 4 a is a detail view from the rear, of the upper portion of thereflector panel carriage.

FIG. 5 is a perspective view of one of the solar collector's tworeflector panel frames, shown with attached suspension cable.

FIG. 6 is a perspective view from the front, of one of the solarcollector's two reflector panels, with attached alignment guide.

FIG. 7 is a perspective view from the rear, of the flattop receiver.

FIG. 8 is a perspective view from the rear, of the pot and pan rack,with glare shield in exploded position for clarity.

FIG. 8 a is a perspective view from the rear, of the pot and pan rackarms in alternative position for attached wire saucepan support, andglare shield in exploded position for clarity.

DETAILED DESCRIPTION OF THE INVENTION Features of Example Embodiments

What follows describes two exemplary embodiments of the solar collector(see FIG. 1, FIG. 2 b), with some parts and aspects of the inventiondirected toward those embodiments, for use as a solar cooker. Many usesother than cooking are possible; but cooking is likely to be the mostcommon use.

A flattop receiver can be used as a griddle, or used with flat-bottomedcooking vessels resting on it to be heated by contact similar to asmooth-top stove. Concentrating reflector panels are shown in open,operating position (see FIG. 1, FIG. 1 a). The reflector carriage andreflector panels are also shown positioned for storage (see FIG. 1 b).The main frame is shown with a rolling chassis (see FIG. 2), so that theapparatus is easily moved over a firm, smooth surface, or installed to afixed-location pivot (see FIG. 2 b). There is a novel cable system forconvenient manual altitude adjustment of reflectors (FIG. 3). Mostmaterials used in the preferred embodiment are of relatively low costand widely available. The main frame, reflector carriage, and reflectorframe (see FIG. 5) are of mild steel in standard profiles of tubing,angle and bar. Other features are made of commonly available steel stockand fastener parts such as sheet, rod, cable, bolts, and nuts. Thereflector panels (see FIG. 6) are of thermoformed sheet plastic.

Main Frame

The solar collector has a main frame (FIG. 2) with an essentiallyhorizontal base 200. Base 200 is a length of square tubing. Front andrear axletrees 202, 204 of like material are transversely joined bywelding at their midpoints to the topside of the ends of base 200, toform a chassis. Caster mounting plates 206, 207, 208, 209 are welded tothe underside of axletrees 202, 204 at both of their ends. Swivelcasters 210, 211 are attached by welding to caster mounting plates 206,207. Fixed casters 212, 213 are attached by welding to caster mountingplates 208, 209. A vertical support 220 of square tubing isperpendicularly joined by welding to the front end of base 200. Atransverse member 222 of like material is joined by welding to the upperend of vertical support 220, to form a tee. Risers 224, 225 ofrectangular tubing, are perpendicularly joined by welding to each end oftransverse member 222, and extend further upward. The vertical support220, transverse member 222 and front frame risers 224, 225 together forma wishbone shape at the front of the main frame. A winch support 214,consisting of a piece of steel angle, is attached by welding to the rearside of transverse member 222. Winch support 214 is oriented with itsvertex at the rear upper edge of transverse member 222. The top surfacesof transverse member 222 and winch support 214 provide a mounting areafor a winch 300 (FIG. 3).

Receiver arms 226, 227 of rectangular steel tubing are joined by weldingto the rear faces of front frame risers 224, 225 at the top. Receiverarms 226, 227 extend horizontally rearward toward the focal area of theconcentrator, and terminate on opposite sides of the center of the focalarea. Frame pivot bushings 228 a, 229 a (see FIG. 2 a) are set intoconcave, semicircular cutouts in the sides of each end of receiver arms226, 227 and attached transversely to them by welding. Frame pivotbushings 228 a, 229 a are steel and serve as sleeve bearings, carryingsteel pivot bolts 241 a, 242 a. Pivot bolts 241 a, 242 a serve asrotational center pins, around which the reflector carriage (see FIG. 4)pivots. Steel lock nuts 249 a, 250 a are threaded onto the ends of thepivot bolts 241 a, 242 a. Steel thrust washers 243 a, 244 a are placedunder the heads of the pivot bolts 241 a, 242 a. Steel thrust washers245 a, 246 a are placed between frame pivot bushings 228 a, 229 a, andcarriage pivot bushings 402, 403 (see FIG. 4). Steel thrust washers 247a, 248 a are placed under lock nuts 249 a, 250 a.

Receiver support rails 232 a, 233 a are lengths of steel angle withvertices aligned to the inner, lower edges of receiver arms 226, 227,and attached by welding to the inner sides of receiver arms 226, 227.Receiver retainers 236 a, 237 a (see FIG. 2 a) are short pieces of steelangle with vertices aligned to the upper, inner edge of the receiverarms 226, 227 and attached by welding to the inner side of receiver arms226, 227 near their front ends. The horizontal sides of receiverretainers 236 a, 237 a each have an inner and an outer hole. Retainerbolts 234 a, 235 a are placed in either the two inner or the two outerholes, to retain either the flattop receiver (see FIG. 7) or the pot andpan rack (see FIG. 8) respectively, in proper position at the focal areaand prevent it sliding and tipping during operation of the solarcollector.

Altitude Cable System

The altitude cable system (FIG. 3) of the preferred embodimentfacilitates manually raising, lowering and holding the reflectors inposition, and is operated by a hand-crank winch 300. Winch 300 is awidely available standard product, made of steel and often supplied witha length of steel cable pre-attached to the reel. Winch 300 is mountedby welding upon winch support 214 and transverse member 222 of the mainframe.

Steel altitude cable 310 passes from winch 300 downward to a commonsteel primary pulley 320, which is attached to the main frame at thefront end by a common bolt and nut 322 through front axletree 202 andbase 200. Primary pulley 320 provides an approximate right-angledirectional change of altitude cable 310, which then passes horizontallytoward the rear of the main frame to secondary pulley 330. Secondarypulley 330 is attached to the main frame at the rear end by a commonbolt and nut 332 through rear axletree 204 and base 200, and changes thedirection of altitude cable 310, so that it courses back toward thefront of the main frame. Altitude cable 310 bends upward around thelower front edge of lower carriage arm front brace 408 (See FIG. 4).FIG. 3 shows cable 310 coursing upward from the bend, though lowercarriage arm front brace 408 is not pictured. Altitude cable 310 isattached terminally to eyebolt 340, which passes up through holes in thetop and bottom faces of upper carriage brace 404, and is held in thatposition, eye-end down, by a common lock nut (see FIG. 4.) Uppercarriage brace 404 is not pictured in FIG. 3.

Reflector Carriage

The reflector carriage (see FIG. 4) has two upper carriage arms 400, 401of rectangular steel tubing which are parallel to, and lie outside of,the main frame's receiver arms 226, 227, when in storage position.Carriage pivot bushings 402,403 are set into concave, semicircularcutouts in the sides of each rear end of upper carriage arms 400, 401and attached transversely to them by welding. Carriage pivot bushings402,403 are coaxial with frame pivot bushings 228 a, 229 a and serve assleeve bearings around pivot bolts 241 a, 242 a (see FIG. 2 a). Pivotbolts 241 a, 242 a pass through the pairs of adjacent frame and carriagepivot bushings on each side of the focal area. The reflector carriage isthus suspended from the main frame by pivot bolts 241 a, 242 a.

Upper suspension cable ears 451 a, 452 a (see FIG. 4 a), are shortpieces of steel angle attached by welding to the outer faces of uppercarriage arms 400, 401 adjacent to their rear ends. Suspension cablerings 453 a, 454 a each pass through a hole in the upper suspensioncable ears 451 a, 452 a and help to equalize tension in each reflectorframe suspension cable 530 (see FIG. 5).

At the front ends of upper carriage arms 400, 401, front carriagemembers 410, 411 (see FIG. 4) of like material are attachedperpendicularly by welding. Upper carriage brace 404 of square steeltubing is attached perpendicularly by welding, to connect front carriagemembers 410, 411 in the upper third of their height. Eyebolt 340 of thealtitude cable system (see FIG. 3), is attached, eye-end down, with acommon locknut approximately midway along the length of upper carriagebrace 404 through holes in the top and bottom. Front panel stops 412,413 of square steel tubing are attached perpendicularly by welding tothe outside surface of front carriage members 410, 411 just above theirlower ends.

Lower carriage arms 420, 421 of rectangular steel tubing are attached bywelding to the rear faces of front carriage members 410, 411 at theirlower ends. Lower carriage arms 420, 421 extend rearward, parallel toupper carriage arms 400, 401. Rear carriage risers 426, 427 of likematerial are joined perpendicularly by welding to the topside of lowercarriage arms 420, 421, at their rearward ends, extending vertically.Rear panel stop 430 of square steel tubing is attached perpendicularlyby welding to the top ends of rear carriage risers 426, 427, bracingthem and extending laterally beyond them. Each reflector panel (see FIG.6) rests against one end of rear panel stop 430, and against one offront panel stops 412, 413, when folded to storage position (see FIG. 1b).

Front and rear hinge-mounting plates 444, 446 are attached by welding tothe underside of lower carriage arm 420. Front and rear hinge-mountingplates 445, 447 are similarly attached to the underside of lowercarriage arm 421. Lower carriage arm front brace 408 of square steeltubing is perpendicularly attached by welding to connect the inner sidesof lower carriage arms 420, 421, near front hinge-mounting plates 444,445. Lower carriage arm rear brace 416 of square steel tubing issimilarly attached to connect the inner sides of lower carriage arms420, 421, near rear hinge-mounting plates 446, 447.

Reflector Panel Frames

A reflector panel frame (see FIG. 5) is disposed on each side of thesolar collector, constructed of square steel tubing and rectangular bar.All parts are joined by welding. Each reflector panel frame isapproximately in the shape of a square overall, with truncation of thetwo corners nearest lower carriage arms 420, 421. This truncationprovides clearance of the chassis and ground when the reflectors arerotated for altitude adjustment. Along the sides of each reflector panelframe are a plurality of holes drilled through the top and bottom faces,to provide for mounting of the reflector panels (see FIG. 6) with commonfasteners.

Reflector panel frame short side 500 extends between the truncatedcorners. Reinforcing plates 502, 503 of steel bar are attached bywelding near the ends of reflector panel frame short side 500. Hinges504, 505 are attached by welding one leaf to the reinforcing plates 502,503. The other leaf of hinges 504, 505 is attached by welding tohinge-mounting plates 446, 444, 445, 447 of lower carriage arms 420, 421(see FIG. 4). Hinges 504, 505 thus serve as pivoting lower supports forthe reflector panel frames, allowing them to be folded upright tostorage position (See FIG. 1 b).

Truncation segments 510, 511 are joined at 45-degree angles to the innersides of short side 500, and to reflector panel frame front and rearsides 512, 513. Reflector panel frame front and rear sides 512, 513 havea plurality of holes through their top and bottom faces for the mountingof a reflector panel (see FIG. 6). Cross brace 515 is perpendicularlyattached by welding to connect the inner faces of reflector panel framefront and rear sides 512, 513. Lower suspension cable ears 516, 517 ofsteel bar are attached to the outer faces of the front and rear sides512, 513 approximately midway between cross brace 515 and upper, outerreflector panel frame side 520. Lower suspension cable ears 516, 517have holes in their upper ends to permit attachment of suspension cable530. Suspension cable 530 is adjusted and fixed at the properpredetermined length using common cable clamp, 531. In operatingposition, the reflector panel frames are thus suspended from uppercarriage arms 400, 401 at a predetermined operating angle of inclinationwith front carriage members 410, 411. Storage ear 525 of steel bar isattached to the outer face of upper, outer panel frame side 520 near itsmidpoint. Storage ear 525 has a hole at its upper end. When thereflector panel frames are folded to storage position, storage ear 525of each reflector panel frame thus provides an attachment point for acommon lanyard, to keep the two reflector panel frames folded upright.FIG. 1 b shows an example of a common type of elastic lanyard.

Reflector Panels

The solar collector in the example embodiments has a reflector panel(see FIG. 6), disposed on each side (see FIG. 1), mounted upon areflector panel frame. The reflector panels are each of one piece,formed from a single sheet of plastic material. They are mounted to eachreflector panel frame using common fasteners through holes along theplanar, perimetric reflector panel border 630, corresponding in positionto the mounting holes in each reflector panel frame side 512, 513 (seeFIG. 5). The reflector panel has a plurality of square reflector-mountsurfaces 600, each individually orientated such that when the reflectorpanels are properly aligned to incoming rays of solar energy, flatreflective material mounted upon the reflector-mount surfaces 600 willreflect the rays to the solar collector's focal area, where it isabsorbed by a receiver. The reflector-mount surfaces 600 are joined toeach other by a multitude of triangular connecting surfaces 610.

An alignment guide of steel plate and rod, with an alignment guide baseplate 620 and shadow peg 622, is mounted with mastic of uniformthickness upon a broad portion of reflector panel border 630, adjacentto a truncated corner, at the front of the solar collector. In thislocation base plate 620 has the same predetermined angle of inclinationas the reflector panel frame has with front carriage members 410, 411.The shadow peg 622 is attached to the base plate 620 longitudinallyparallel to front carriage members 410, 411. The alignment guideprovides a safe and comfortable visual reference for the user, allowingthe reflector panels to be adjusted properly toward the sun without theuser gazing at the intensely bright focal area.

Process for Making the Fresnel Array Reflector Panel

Using techniques well known to those skilled in the art of computeraided design (CAD), computer software is used to generate a data filethat defines the three dimensional (3D) shape of a Fresnel arrayconcentrating reflector panel that accepts a plurality of pieces of flatreflector material.

Initially, a focal area is defined in 3D space, by drawing andspecifying the portion of a solar collector apparatus that will locateand support a receiver of concentrated solar energy at the focal area.Similarly the overall size, shape and location of the reflector panel isdefined in space by drawing the reflector carriage, (the portion of asolar tracking collector apparatus that carries the reflector panelthrough the range of travel needed altitude adjustment duringoperation.) All intermediate connecting structure between the receiverand reflector panel must also be drawn to define the relative positionsof the focal area and reflector panel. At the end of this process, thereflector panel's geometric center and the center of the focal area mustlie in a common vertical plane that is normal to the vertical plane ofrotation of the reflector carriage.

It is generally desirable to minimize the degree of material “stretch”and stress, in forming a 3D shape from a flat sheet. This is one reasonwhy the reflector panel is inclined toward the focal area duringoperation. Another reason for reflector panel inclination is to reducethe degree of interference between the reflectors in the Fresnel array(the high side of a reflector blocking some of the light reflected fromthe low side of an adjacent reflector.)

For purposes of design, it is assumed that rays of sunlight all travelalong the vertical axis (as from a directly-overhead sun.) The angle ofinclination of the reflector panel is that which causes a vertical rayof sunlight incident upon the geometric center of the panel to bereflected through the center of the focal area. The law of specularreflection is used to determine the angle of inclination of thereflector panel. The acute angle of incidence between a vertical ray andthe inclined panel must equal the acute angle between the panel and thereflected ray. The reflector panel is rotated about the axis of itsattachment to the carriage until this requirement is satisfied.

Individual mount surfaces are initially drawn in the same plane as theperimetric border of the panel, which is maintained with sufficient areato provide a mounting face that can serve to mount the reflector panelupon a supporting frame. The size of individual flat reflectors andtheir corresponding mount surfaces is determined by the size of thedesired focal area for the receiver, with the mount surfaces beingsmaller than the focal area to account for distortion in reflection andfocal precision. The number of mount surfaces in the panel is estimatedinitially, and can be adjusted later if needed, after checking forinterference between reflectors and adjusting the spacing between them,to eliminate any interference found. Alternatively, the overall size ofthe reflector panel can be adjusted to accommodate a given number ofmount surfaces.

In accordance with the law of specular reflection, each mount surface isindividually rotated about its geometric center, so that a vertical rayof sunlight striking the geometric center is reflected to the center ofthe focal area. The degree of tilt needed for each mount surface to meetthat criterion increases with its distance from the center of the panel.This often entails interference between adjacent reflectors, increasingwith distance from the center of the panel. To avoid blocking, adjacentmount surfaces are spaced further from each other, as distance from thecenter of the panel increases. After each mount surface is tiltedproperly for reflection to the focal area, the degree of interferencecan be assessed by drawing rays from the lower, outer edges of thereflector mount surface parallel to the alignment ray passing throughits geometric center. If a mount surface is moved to eliminateinterference, it is moved along the plane of the reflector panel, so allmount surfaces will have coplanar geometric centers. After each suchmove, the mount surface must be re-tilted for focal alignment andrechecked for interference, until interference is eliminated.

The above CAD process results in a 3D digital model of the reflectorpanel form in which each mount surface is a Fresnel approximation ofpart of an elliptic paraboloid. In this embodiment the geometric centersof all mounting surfaces remain coplanar with the perimetric border ofthe reflector panel, for a relatively flat, compact storage profile.

The CAD data file produced is used to guide Computer Numeric Control(CNC) machining, whereby molds or dies suitable for forming the Fresnelreflector panel are produced, using methods well known to those skilledin the art of mold making Using methods well known to those skilled inthe art of plastic thermoforming, the reflector panel of the preferredembodiment is then formed from a sheet of heated plastic placed over themold and drawn into a conforming shape. For cost reasons, it iscontemplated that Acrylonitrile Butadiene Styrene (ABS) plastic will beused, though many other types and combinations of plastic sheet areusable. Flat reflective material of various types can then be adhered toeach mount surface of the panel with a suitable adhesive applied inuniform thickness, resulting in a concentrating reflector array for usewith the predefined solar apparatus.

Flattop Receiver

The flattop receiver (see FIG. 7) of the preferred embodiment is cast asone piece of aluminum, using techniques well known to those skilled inthe art of metal casting. A heat transfer or cooking surface is providedas the topside of an oblong, flat plate 700. The longer edges of flatplate 700 rest upon receiver support rails 232 a, 233 a (FIG. 2 a) ofthe solar collector's main frame. Flat plate 700 is semicircular at therear end, and rectangular at the front end, corresponding to the rearand front ends of the solar collector's main frame.

The top side of flat plate 700 has a raised edge 710 along itsperimeter. Raised edge 710 is taller at the semicircular end, near thefocal area. This taller portion prevents food that is cooked directly onflat plate 700 from being scorched by exposure to concentrated solarenergy and provides an absorbing surface for that energy, when the sunis at lower altitudes, and the solar concentrator's reflector panels aremore elevated. Raised edge 710 also generally serves to retain cookingoil, food and liquid, and to catch spatter when the flattop receiver isused as a griddle. In operating position the semicircular, rear portionof flat plate 700 extends past the rear ends of receiver support rails232 a, 233 a, and beyond the center of the focal area. Retainer bolts234 a, 235 a (see FIG. 2 a) extend down into the corners formed by thefront end of the rectangular portion of raised edge 710. This retainsthe receiver in proper position relative to the focal area and preventsthe flattop receiver tipping up at the front end and falling, if a heavyload is placed at the semicircular rear end.

From the underside of flat plate 700, a hollow, tubular energy absorber720 extends downward through the focal area. When the sun is at higheraltitudes, energy absorber 720 receives most of the concentrated energyreflected to the focal area. Heat is conducted quickly from energyabsorber 720 to the topside of flat plate 700 for direct use in cooking,or for heating smaller flat-bottomed vessels.

Pot and Pan Rack

In place of the flattop receiver shown in FIG. 1 and FIG. 7, commoncooking pots may be placed into the focal area using an adjustable potand pan rack (see FIGS. 8, 1 a and 1 b). The pot and pan rack is mainlyof steel square tubing and bar. In use, rack sides 811, 812 rest uponreceiver support rails 233 a, 232 a (see FIG. 2 a). Front cross member800 and a rear cross member 810 are joined perpendicularly by welding toconnect the inner faces of rack sides 811, 812. Stabilizer bushings 803,804 are joined by welding to the top of rack sides 811, 812 at the frontend, to receive retainer bolts 235 a, 234 a, and to bear against theunderside of receiver retainers 237 a, 236 a. Thus the pot and pan rackis retained in proper position relative to the focal area, and does nottip up at the front when a heavy load is placed at the rear (focal) end.Rack risers 821, 822 feature a multitude of holes in their front andrear faces, and are joined perpendicularly by welding to the rear endsof rack sides 811, 812. Each hole in the front face of a rack riser hasa corresponding hole in the rear face, vertically aligned to a commonhorizontal axis. Rack collars 831, 842 are short pieces of steel squaretubing with inner dimensions slightly greater than the outer dimensionsof rack risers 821, 822. Each collar has a hole in its front and in itsrear face, one vertically aligned with the other, on a common horizontalaxis. The rack collars 831, 842 can thus be slid up and down over theoutside of rack risers 821, 822, and secured in various positions byaligning the holes of rack collars 831, 842 with those of rack collars831, 842 at the desired height, and passing a common bolt or hitch pinhorizontally through. Rack arms 830, 840 are of steel bar, attached bywelding to the outer faces of rack collars 831, 842. Each rack arm 830,840 extends rearward over each side of the focal area, and has a curved,concave cutout along its upper edge to help retain the diametricallyopposed handles of common stockpots. Stockpot handles rest upon rackarms 830, 840, so that the lower portion of the stockpot is suspended inthe focal area of the solar collector. Rack collars 831, 842 can belaterally switched in position (compare FIGS. 8 and 8 a) so that rackarms 830, 840 extend from the inner faces of rack collars 831, 842. Thisalternate configuration can accommodate smaller stockpots, as rack arms830, 840 are nearer each other. Each rack arm 830, 840 also has a pairof holes, from which saucepan support 860 a (see FIG. 8 a) can besuspended in the alternate configuration. Saucepan support 860 a is offormed and spot-welded steel wire, and can support pans that have only asingle handle.

Glare shield 850 of sheet metal is attached to the upper face of racksides 811, 812 with common fasteners, to reduce user exposure to lightdiffusely reflected from the various pots and pans that may be used withthe rack.

Operation of the Preferred Embodiment

When the solar collector is in storage position, the reflector panelsare folded upright, resting against the panel stops 412, 413, 430 at thefront and rear of the apparatus. A common lanyard or shock-cord attachedto storage ear 525 of each reflector panel frame can be used to hold thereflector panels in storage position (see FIG. 1 b). To use the solarcollector, it must be in a sufficiently large, open area receivingdirect sun. A single adult user of average strength can roll the solarcollector into position across a smooth, level surface by pulling thesolar collector by the crank handle of winch 300 or by frame frontrisers 224, 225. Detaching the lanyard from one storage ear 525, thereflector panels can be opened outward and down, pivoting on hinges 504,505 to operating position, supported by hinges 504, 505 and suspensioncable 530.

Either the flattop receiver of FIG. 7 or the pot and pan rack of FIGS. 8and 8 a can be chosen by the user, depending on the type and amount ofcooking to be done. The flattop receiver of FIG. 7 provides a smoothcooking surface of about ½ the area of a standard 4-burner stove top.The receiver allows direct frying as on a griddle, or the heating ofsmaller flat-bottom cooking vessels upon its surface, similar to asmooth-top electric stove. The pot and pan rack adjusts to acceptvarious stock pots or saucepans, which then receive direct concentratedsolar energy themselves. This arrangement may be more suitable forlarger quantities of food, or when weather conditions provide less sunto the solar collector. Either the flattop receiver or the pot and panrack is placed upon receiver support rails 232 a, 233 a. The flattopreceiver is positioned so that retainer bolts 234 a, 235 a can beinserted down through the inner two holes in receiver retainers 236 a,237 a and into the front corners of the receiver. This prevents thereceiver sliding forward or tipping up at the front and falling off therear end of support rails 232 a, 233 a. If the pot and pan rack is used,it is similarly positioned with retainer bolts 234 a, 235 a passing downthrough the outer two holes in receiver retainers 236 a, 237 a and intostabilizer bushings 803, 804.

Standing at the front of the solar collector, a user can quickly andcomfortably observe the alignment of the solar collector with the sun,by observing the shadow cast by the alignment guide's shadow peg 622.The shadow of the peg becomes invisible, falling directly under the pegitself rather than onto base plate 620, when the solar collector isadjusted to produce maximum heat. As the sun's position relative to theearth changes, the peg's shadow reappears upon base plate 620,indicating the need and direction for readjustment, in order to maximizethe heat produced. The solar collector's positional adjustments are madeat 10-20 minute intervals during operation to maintain the amount ofenergy reaching the receiver.

Altitude is adjusted by turning the hand-crank winch 300, which alsoholds the reflectors in position following adjustment. When altitudecable 310 is drawn in by winch 300, the reflector carriage and attachedreflector panels move in a rearward and upward direction, rotating aboutpivot bolts 241 a, 242 a and the focal area that lies between them. Whenaltitude cable 310 is paid out, the reflector panels descend toward thefront of the solar collector by virtue of their own weight. The altitudecable system, together with the main frame of the concentrator, canprovide 90 degrees reflector rotation, though the fullest extent ofrotation would rarely be useful (unless the user is commonly warmingfood on a mountaintop at sunrise or sunset.)

Azimuth adjustments are made using the crank handle of winch 300 to rollthe front end of the solar collector sideways, facilitated by swivelcasters 210, 211. This can be quickly and easily done, simultaneouslywith altitude adjustment. The alignment guide also indicates the properdirection and degree of azimuth adjustment needed.

An adult user of ordinary physical size and capability can convenientlyand easily make azimuth and altitude adjustments at the same time, withone hand, from the same position in which cooking activity is performed.Adjustments do not require a user to reach near or past the focal areaor hot cooking vessels. There is no need to drag or tilting theconcentrator and cooking vessels for reflector adjustment, so tipping,spillage or dislodgement of cooking vessels is not a problem. If a userfails to make timely altitude and azimuth adjustments, the amount ofheat received will decline, as the relative position of the sun changesand reflector focus is lost. This naturally prevents food being burnedduring cooking, and prevents waste. If less heat is desired duringcooking, attenuation can be obtained by maintaining an alignment guidepeg shadow of varying length; a longer shadow corresponds to less heat.Other ways to reduce the amount of heat reaching the food being cookedinclude: Moving the food or cooking vessels further from the focal endof the receiver, draping a cloth over some of the reflectors, or mistingwater onto the receiver.

Additional Embodiment: Stationary Installation

The solar collector may also be configured for a fixed location, with afew physical differences from the preferred embodiment, as describedbelow. FIG. 2 b shows an exemplary embodiment, for ground installation.

Front pulley 262 b and rear pulley 264 b serve respectively in place ofprimary pulley 320 and secondary pulley 330 of the first exemplaryembodiment, in the otherwise identical altitude cable system. A square,steel base plate 270 c (see FIG. 2 c) is attached by welding to theunderside of base 200, approximately midway along its length. Base plate270 c has holes for common fasteners at its four corners.

For stationary installation, an outer sleeve 279 c, being a length ofsteel pipe with bottom end plugged, is set plumb in an excavation withdepth sufficient to provide a stable, solid base for the solarcollector. Concrete footing 260 b is poured into the excavation aroundouter sleeve 279 c and given time to cure. An inner sleeve 278 c, beingsteel pipe with somewhat shorter length than outer sleeve 279 c, andwith an outer diameter slightly smaller than the inner diameter of outersleeve 279 c, is centered on one side of pivot plate 272 c, and joinedperpendicularly to it by welding. Pivot plate 272 c is otherwiseidentical to base plate 270 c. Debris shield 276 c, being a short pieceof steel pipe with inner diameter slightly larger than the outerdiameter of outer sleeve 279 c, is slid to a concentric position overinner sleeve 278 c and against pivot plate 272 c, and joinedperpendicularly to the pivot plate 272 c by welding. The debris shield276 c serves to exclude rain, dirt and debris from the space betweeninner sleeve 278 c and outer sleeve 279 c.

Pivot plate 272 c, in solid assembly with inner sleeve 278 c and debrisshield 276 c, is then bolted to base plate 270 c of the solarcollector's main frame, with common fasteners. The main frame of thesolar collector can then be set into position by sliding inner sleeve278 c down into outer sleeve 279 c, so that debris shield 276 csurrounds the upper end of outer sleeve 279 c. The steel parts belowbase plate 270 c collectively provide a simple, durable bearing for aground-based pivot to provide for support and rotation of the entiresolar collector.

Operation of the Additional Embodiment: Stationary Installation

In the exemplary embodiment for stationary installation of the solarcollector described above, operational differences are minimal. Instorage position, the user may wish to cover the solar collector with aprotective tarp, as it will remain outdoors. In operating position,azimuth adjustments are made by grasping the handle of the winch 300 andturning the solar collector sideways, about its ground-based pivot. Allother aspects of operation are unchanged from the first exemplaryembodiment.

Conclusion, Ramifications and Scope of Invention

The exemplary embodiments of my solar collector apparatus describedabove describe just two of many possible embodiments of the invention.Details in the above descriptions were chosen for simplicity, low costand ease of solar collector construction, using relatively limitedresources. Below are discussed some of many possible variations in theinvention. These possibilities should help to show that the scope of theinvention should be determined by the elements of the claims and theirlegal equivalents, rather than by the particular details chosen forspecification of exemplary embodiments.

Alternative Materials, Methods:

Tubing profiles named in the above specifications may be varied withminor design consequences, many different types of tubing or solid stockcan be used, with many different possible profiles, such ascross-sections that are oblong, rectangular, rounded, or convoluted. Onematerial alternative to steel is aluminum. More costly, but lighterweight and more resistant to corrosion by weather exposure, nearly everypart of the solar collector that is specified in steel could be renderedin aluminum. Fiber-reinforced plastic is another alternative material ofwhich many parts could be made. Assembly could involve various joiningbraces or fittings, rivets or other fasteners, or brazing rather thanjoining parts by welding.

The reflector panels (specified in ABS plastic) could be made of sheetaluminum or other pure or alloyed metal, pressed or stamped betweenopposing dies. There are also many different types of plastic, andcombinations of different types, that could be used to form thereflector panels from extruded sheet. An obvious alternative process inthe method for making them could use the CAD data file to machine moldsfor the formation of the reflector panels by injection moldingtechniques, rather than thermoforming. Another type of mold could bemade to fabricate the reflector panels from fiberglass.

There are various coatings available that could be applied to plastic orto metal parts for weather resistance. Stainless steel could be used forcable and other higher-stress parts such as the winch, for greaterdurability and to reduce the need for weather protection andmaintenance.

Design:

The design of the solar collector could be modified in many ways. Forexample the overall frame and reflector carriage could be modified to acurved side-view profile, so that rather than a rectangular shape, theywould have a rounded “C” shape, produced by casting or bent-tubeconstruction. Many possible shapes could meet the requirement for themain frame and reflector carriage, that there be clear passage for lightfrom reflectors to the focal area, throughout the range of reflectorrotation. The reflector carriage design may echo the shape of the mainframe or be rendered as a closed rectangle (seen in some prior art), orclosed or open ovoid, circular or irregular shape.

The overall shape of the reflector panels could be varied, also. Theexemplary embodiment, having reflector mount surfaces with coplanargeometric centers, favors minimizing the overall depth of the reflectorpanel, but tends to increase the amount of stretch required from thematerial to be formed. It would also be possible to minimize materialstretch by placing the geometric centers of the mount surfaces indifferent planes, and reduce interference among reflectors, making theoverall contour of the reflector panel somewhat concave when viewed fromabove. Mount surfaces could be made concave to conform to applicableconcave reflectors.

The altitude cable system could be simplified, using just one pulley orother direction-changing device like a simple half-ring cable guide, atthe bottom of the vertical support 220, for a direction reversal of thecable so it courses back up to the transverse member 222 or to a higheror otherwise different anchor point. This would decrease the range ofcarriage travel, and add physical strain in the mechanism and carriage,but still allow elevation through much of the usable range of reflectorrotation. Pulleys could be replaced with various forms of plastic ormetal cable guides, even by simple holes drilled in the frame.

Many other parts could also be varied from those specified. Fixedcasters could be replaced with wheels mounted on the ends of a fixedaxle. Swivel casters could be replaced with some variation of a pivotingaxle and fixed wheels, as is commonly seen on a child's wagon. Axletreescould be lengthened or otherwise modified in form, or the height of themain frame could be increased, to accommodate larger wheels, makingtransport across rough terrain easier. The location and shape of cableattachment ears could be varied. Small tension-equalizing pulleys couldbe used instead of the suspension cable rings, or the rings could simplybe eliminated. Bracing among main frame or reflector frame members couldbe varied in position or form, in many different ways. The flattopreceiver's energy absorber could have a variety of different shapes,such as an X-shaped or I-shaped or S-shaped cross-section, as examples.The rear end could be rectangular rather than rounded, oval rather thansemicircular, etc.

Efficiency:

The efficiency of the solar collector could be improved by reducing heatlosses, using a greenhouse effect, and insulation. The focal area couldtrap collected heat with a receiver enclosure having glass sides, andbottom, or a heat-reflective, insulating bottom. Addition of insulatingmaterial to the front portion of the flattop receiver would also tend toincrease available heat. For example, a removable top side insulatorcould be placed over the front portion of the flattop receiver when notin use, or over the entire top surface for preheating. A fixed layer ofinsulation could be added to the area immediately under the frontportion of the flattop receiver, between the receiver arms, leaving sunstruck areas of the energy absorber exposed, of course. Insulationstrips between the receiver support rails and the side edges of theflattop receiver would also reduce heat loss to the solar collectorframe by avoiding metal-metal contact. There is also the possibility ofadding a third, smaller reflector frame and panel, deployed beyond therear end of the main frame, having rigid bracing to prevent it tippingforward upon elevation. Rigid bracing could also be added between theexisting reflector frames and main frame, to prevent wind causing themto fold toward storage position during operation, when the wind isstrong enough to overcome the weight of the reflector frames and panels.

Uses:

The preferred embodiment of the solar collector is designed primarilyfor cooking; but its utility can be easily extended beyond cooking Solarthermal energy concentrated by a smaller, point-of-use solar collectorhas many possible uses that require the presence of an attendant forother tasks, making the additional task of manual adjustmentsinsignificant as an added labor cost. The manual task of performingaltitude and azimuth adjustments adds no significant burden to many suchactivities. For example, a receiver in the form of a boiler would permituse of the solar collector to power a steam cleaner with a flexible hoseand wand, such as is currently available to consumers as an electricappliance. Steam produced could be used in an autoclave to sterilizemedical instruments, or to kill weeds, to preserve and can food, or torun a small steam engine powering various tools or processes.Distillation is another process using heat that could be powered in adistributed fashion, such as for the production of ethanol fuel.

Scale:

There is potential for scaling up in size that would serve many of theabove alternative uses well. Multiple Fresnel panels could be producedand combined upon a larger supporting frame, for a larger reflectoraperture and an increase in collected energy. I estimate that a singleuser could perform manual two-axis tracking without much modification tothe present design, scaled to a reflector area increase by a factor offour. The solar collector could also be scaled down, for more compactstorage and a smaller operating area.

Thus there are many possible modifications and variations as well asimprovements on the invention, and it is apparent that the claims andtheir elements have many legal equivalents.

I claim:
 1. A concentrating collector of solar energy, comprising: (a) a main frame having an elongated vertical support fixedly attached to a ground-based pivot with a vertical axis of rotation, said main frame further having a front end and a rear end, said vertical support being located at said front end, said front end being immediately adjacent to the location where a user of said concentrating collector of solar energy stands to perform altitude and azimuth adjustments, said front end of said main frame having a mounting location for a winch, said main frame further having two horizontal, elongated receiver support arms extending from said front end toward said rear end, said receiver support arms terminating on opposite sides of a focal area where rays of reflected solar energy reach their closest convergence, each said receiver support arm having one of two frame pivots on opposite sides of said focal area, said frame pivots further having a common horizontal axis of rotation, (b) a reflector carriage suspended from said main frame at said frame pivots, said reflector carriage having a storage position that also permits operation of said concentrating collector of solar energy when the sun is directly overhead, said reflector carriage requiring rotation about said frame pivots toward and from said rear end, to permit operational altitude adjustment of a plurality of reflector-mount surfaces when the sun is at lower altitudes, said ground-based pivot permitting rotation of said reflector carriage together with said main frame about a vertical axis, for azimuth adjustment of said plurality of reflector-mount surfaces, (c) a means for controllably rotating and holding said reflector carriage about said frame pivots with said winch, further comprising an altitude cable and at least one pulley to effect directional change of said altitude cable, and (d) a receiver located at said focal area to absorb concentrated solar energy, whereby a user standing before said front end of said main frame can easily maintain proper orientation of said plurality of reflector-mount surfaces toward the sun, so that following the mounting of reflectors to said plurality of reflector-mount surfaces, said concentrating collector of solar energy causes reflected solar energy to converge at said focal area and be absorbed by said receiver during operation.
 2. The concentrating collector of solar energy of claim 1, wherein said ground-based pivot comprises (a) an elongated horizontal base attached to said vertical support at said front end of said main frame and extending to said rear end, said elongated base having a top side and a bottom side, and (b) a bearing attached to the bottom side of said base, whereby said concentrating collector of solar energy can be horizontally rotated for azimuth adjustment, said ground-based pivot can be attached to said base at a point minimizing the potential for wind to cause unwanted rotation, and said concentrating collector of solar energy is vertically supported for installation in a fixed location.
 3. The concentrating collector of solar energy of claim 1, wherein said ground-based pivot comprises (a) an elongated horizontal base attached to said vertical support at said front end and extending to said rear end of said main frame, (b) a plurality of axletrees with attached casters, substantially forming a rolling chassis that is steerable at said front end and provides a base of support upon a ground surface for said concentrating collector of solar energy, whereby said front end can be easily rolled from side to side to pivot the concentrating collector of solar energy about a vertical axis of rotation near said rear end for azimuth adjustment of said plurality of reflector-mount surfaces, and said concentrating collector of solar energy can be easily transported.
 4. The concentrating collector of solar energy of claim 1, further including a plurality of reflector frames to help support said plurality of reflector-mount surfaces, said reflector frames having hinges that attach to said reflector carriage, so that said reflector frames and said plurality of reflector-mount surfaces are foldable to an upright storage position, whereby said plurality of attached reflectors are protected against weather and soiling, and said concentrating collector of solar energy has a more compact profile for storage.
 5. The concentrating collector of solar energy of claim 1, wherein said receiver rests upon said receiver support arms and has a shape comprising (a) an oblong flat plate with a top side and a bottom side, (b) a raised edge above and along the perimeter of said top side, (c) a protuberance extending downward from said semicircular end of said bottom side and through said focal area to function as an energy absorber, whereby following the mounting of reflectors to said plurality of reflector-mount surfaces reflected convergent rays of solar energy are absorbed by said protuberance and by said bottom side and by said raised edge at various times during operation of said concentrating collector of solar energy, resulting in heat accumulating and being conducted to said top side, where flat-bottomed cooking vessels can be placed for heating or food may be directly cooked, as upon a griddle.
 6. The concentrating collector of solar energy of claim 1, further including an adjustable rack that rests upon said receiver support arms, said rack comprising (a) a frame having sides that rest upon said receiver support arms and extend toward said rear end, each said side having a rearward termination at a point of attachment to (b) a vertical rack riser of rectangular tube having a plurality of positioning holes through two sides, regularly spaced in a column along its height, each said rack riser accepting a (c) rack collar of rectangular tube that fits around said rack riser and can slide up and down around said rack riser, each said rack collar further having a hole through two sides, each said rack collar further having attached to one side a rack arm extending over and to one side of said focal area to support said receiver, said rack arm also being able to suspend an additional receiver support made of wire and able to hold a smaller said receiver, whereby a user can set both rack collars to a desired height by passing a common bolt or hitch pin through said hole in each said rack collar and through one of the said plurality of positioning holes in each said rack riser, to suspend at said focal area a cooking vessel taken from a group containing various different sizes and shapes of cooking vessels, to serve as said receiver of said concentrating collector of solar energy.
 7. The concentrating collector of solar energy of claim 1, further including a reflector panel that is formed as a single piece of moldable material, comprising: (a) said plurality of reflector-mount surfaces discretely disposed, each said reflector-mount surface having a predetermined spatial orientation, (b) a plurality of connecting surfaces between said reflector-mount surfaces to ensure their stability of position, and (c) an area of said material to allow fixedly attaching said reflector panel to a supporting frame that is attached to said reflector carriage, whereby said reflector panel provides support and predetermined positioning for reflective material to be applied to said plurality of reflector-mount surfaces, so that following the mounting of said reflective material to said plurality of reflector-mount surfaces, and with proper orientation of said reflector panel toward the sun, said reflector panel causes sunlight incident upon said reflective material to be reflected to said focal area.
 8. The concentrating collector of solar energy of claim 1, further including a solar alignment guide comprising (a) an alignment guide base plate, attached to a part of said concentrating collector of solar energy that moves with said plurality of reflector-mount surfaces, and (b) an upright, elongated shadow peg attached at an angle to said alignment guide base plate so that, following the mounting of reflectors upon said plurality of reflector-mount surfaces, said shadow peg is longitudinally oriented parallel to rays of sunlight incident upon the geometric centers of each said reflector, when said incident rays of sunlight are also specularly reflected through the center of said focal area, whereby a user of said concentrating collector of solar energy may quickly, easily and comfortably assess the need and direction for altitude and azimuth adjustment of said plurality of reflector-mount surfaces by viewing said solar alignment guide, and without gazing at the intense brightness of said focal area.
 9. A reflector panel for use with a concentrating collector of solar energy, said reflector panel being formed of moldable material into a single piece, comprising: (a) a plurality of discrete mounting surfaces for reflective material, each said mounting surface having a predetermined spatial orientation, (b) a plurality of connecting surfaces between said mounting surfaces to maintain the positions and orientations of said mounting surfaces (c) an area of material of said reflector panel for fixedly attaching said reflector panel to a supporting structure, whereby said reflector panel provides support and positioning for reflective material that can be affixed to said mounting surfaces, so that following said fixation of said reflective material to said mounting surfaces, and with proper orientation of said reflector panel toward the sun, said reflector panel causes sunlight incident upon said reflective material to be reflected to a receiver in a predetermined focal area during operation of said concentrating collector of solar energy.
 10. The reflector panel of claim 9, wherein the perimeter of said reflector panel has essentially the shape of a rectangle.
 11. The reflector panel of claim 9, wherein the perimeter of said reflector panel has a shape that is essentially a combination of a rectangle and a circular segment.
 12. The reflector panel of claim 9, wherein each said mounting surface is flat, to accept essentially flat reflector material.
 13. The reflector panel of claim 9, wherein each said mounting surface is concave, to accept concave reflector material.
 14. A method for making a reflector panel formed of moldable material into a single piece, for use with a concentrating collector of solar energy, comprising: (a) using software techniques well known to those skilled in the art of computer aided design (CAD), (b) drawing the structure of said concentrating collector of solar energy that supports and locates a receiver in three dimensional (3D) space, thereby (c) defining a focal area of said concentrating collector of solar energy, (d) drawing the overall size and planar shape of said reflector panel and all structure of said concentrating collector of solar energy that is between said reflector panel and said receiver, including the structure of a reflector panel carriage that carries said reflector panel rotationally about said focal area for altitude adjustment, so that the location of the connection between said reflector panel and said reflector carriage is determined for operation of said concentrating collector of solar energy with a directly-overhead position of the sun, and so that a vertical plane including the center of said focal area and the geometric center of said reflector panel is normal to the vertical plane of rotation of said reflector carriage, (e) subdividing the drawn area of said reflector panel into a plurality of reflector-mount surfaces of predetermined size, leaving space between said reflector-mount surfaces to allow spatial adjustments between them, and leaving space around the perimeter of said reflector panel to allow for attachment to a supporting structure, (f) rotating said reflector panel about its geometric center and through a plane normal to the plane of rotation of said reflector carriage, until a vertical ray incident upon the geometric center of said reflector panel would be reflected through the center of said focal area in accordance with the law of specular reflection, were there flat reflective material covering said reflector panel, (g) individually rotating each said reflector-mount surface about its geometric center for proper focal alignment, so that a vertical ray incident upon the geometric center of each said reflector-mount surface would be reflected through the center of said focal area in accordance with the law of specular reflection, were there flat reflective material covering said reflector-mount surface, (h) checking each said reflector-mount surface for interference with adjacent reflector-mount surfaces by drawing rays from the lower outer edges of said reflector-mount surfaces parallel to the ray from its geometric center through the center of said focal area, (i) moving each said reflector-mount surface through the inclined plane of said reflector panel and further from the interfering said reflector-mount surface to eliminate any interference, and following each such repositioning, again rotating the repositioned said reflector-mount surface about its geometric center as before, and again checking for interference, repeating this cycle of adjustment until interference is eliminated and proper focal alignment maintained for all said reflector-mount surfaces, (j) generating a CAD data file defining the resulting 3D surface of said reflector panel, (k) using methods well known to those skilled in the art of mold making to guide computer numeric control (CNC) machining processes with said CAD data file, to produce molds or dies suitable for forming said reflector panel from moldable material, and (l) using methods well known to those skilled in the art of forming the moldable material, producing said reflector panel with the benefit of said molds or dies. 